Precautions for autoclave

 Precautions for autoclave

Principle of autoclaving

The principle of autoclave sterilization is: in a closed steamer, the steam cannot overflow, and the pressure continues to rise, so that the boiling point of the water continues to increase, so that the temperature in the pot also increases. Under a pressure of 0.1MPa, the temperature in the pot reaches 121°C. Under this steam temperature, it can quickly kill all kinds of bacteria and its principle of high heat resistance


Note: Completely remove the air in the pot so that all the pot is steamed, and the sterilization is complete. There are several different methods of autoclaving and venting, but the purpose is to purge the air, make the temperature of the pot evenly heated, and ensure complete sterilization. The common method is: close the bleed valve, after power on, when the pressure rises to 0.05MPa, open the bleed valve to release air, and then close the bleed valve after the pressure gauge pointer returns to zero. After closing the valve and energizing, when the pressure gauge rises to 0.1MPa, start timing and maintain the pressure at 0.1~0.15MPa for 20 minutes.

 After reaching the holding time, the power supply can be cut off. When the pressure drops to 0.05MPa, the steam can be slowly released. Care should be taken not to reduce the pressure too fast, which may cause intense decompression boiling and overflow the liquid in the container. When the pressure drops to zero, the lid can be opened, the culture medium can be taken out, and placed on the platform for condensation. Don't let the air out for a long time, which will cause the composition of the medium to change, so that the medium cannot be inclined. Once placed for too long, the lid cannot be opened due to the negative pressure in the boiler. As long as the air release valve is opened, the atmospheric pressure is in, the internal and external pressures are balanced, and the lid is easy to open.

 For items that do not deteriorate after autoclaving, such as sterile water, cultivation media, and inoculation equipment, the sterilization time can be extended or the pressure can be increased. The medium must strictly abide by the pressure-holding time. It is necessary to maintain the pressure thoroughly, but also to prevent the ingredients in the medium from deteriorating or reducing the effectiveness. The time cannot be extended at will



1. First take out the inner sterilization barrel, and then add an appropriate amount of water to the outer pot to make the water surface level with the triangle shelf.

2. Put it back into the sterilization barrel and load the items to be sterilized. Be careful not to pack too much, so as not to hinder the flow of steam and affect the sterilization effect. Neither the Erlenmeyer flask nor the end of the test tube should be in contact with the wall of the barrel, so as to prevent the condensed water from drenching the wrapping paper and penetrating the cotton plug.

3. Cover and insert the exhaust hose on the cover into the exhaust slot of the inner sterilization barrel. Tighten the two opposite bolts at the same time in a two-by-two symmetrical manner, so that the tightening of the bolts is consistent and avoid air leakage.

4. Use an electric stove or gas to heat, and at the same time open the exhaust valve to make the water boil to remove the cold air in the pot. After the cold air is completely exhausted, close the exhaust valve and let the temperature in the pot gradually rise as the steam pressure increases. When the pressure in the pot rises to the required pressure, the heat source is controlled to maintain the pressure for the required time. This experiment uses 1.05kg/cm2, 121.3℃, 20 minutes sterilization.

5. When the time required for sterilization is up, cut off the power supply or turn off the gas, and let the temperature in the sterilization pot drop naturally. When the pressure of the pressure gauge drops to 0, open the exhaust valve, loosen the bolt, open the lid, and take out the sterilization article. If the pressure does not drop to 0, open the exhaust valve, and the pressure in the pot will suddenly drop, causing the culture medium in the container to rush out of the mouth of the flask or test tube due to the imbalance of the pressure inside and outside, causing the cotton plug to be contaminated with the culture medium. Pollution.

6. Put the removed sterile medium into a 37°C incubator for 24 hours. After inspection, if there is no bacteria growth, it can be used.

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